Method of coating metallic bodies



Jan. 17, 193:1- g5 EVANT 3,894,644

' METHOD OF COATING METALLIC BODIES Filed June 1929 Patented Jan. 17, 1933 UNITED STATES PATENT OFFICE EARL GROVER STUBDEVANT, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN nnmm COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

mrrrron or con'rmo METALLIC BODIES Application filed June 8, 1929. Serial No. 869,517.

This invention relates to a compound for and method of coating metallic bodies, and more particularly to a compound for and method of insuring theadherence of an insulating coating to a metallic conductor.

An object of the invention is to provide a compound for and method of insuring the adherence of a coating to metallic bodies which will be efficient, practical, and economical.

The invention contemplates the addition to a hydrocarbon insulating compound of an organic acid in such proportion as will insure the creation of a firm bond between the contacting surfaces of the insulating compound and the coated article.

The invention will be understood from the following detailed description read in con nection with the accompanying drawing forming a part thereof, in which Fig. 1 is an elevational View partly in section of an electrical conductor coated in accordance with the invention, and

Fig. 2 is a section taken on the line 22 of Fig. 1.

Referring to the drawing, a solid conductor 10, preferably composed of tinned copper wire. is shown entirely encased by a cylindrical wall of insulating material 11. Since it has been found that the compound to be hereinafter described is effective to produce the desired condition in such cases, any kind lasting bond between the compound and the of electrically conductive metal is permissible for use as a conductor in lieu of tinned copper wire. According to the preferred form of the invention, the compound contains substantial proportions of hydrocarbon substances, such as rubber, paraflins, gutta percha, mineral rubber,'balata, and reclaimed rubber.

For the purpose of creating a firm and conductor, a relatively small percentage of oleic acid is fixed therewith during the preparation of the compound and before the deposition of the compound upon the cor-e. When, in accordance with well known processes of insulating copper wire or other stranded conductors, the compound, in a warm and plastic state, is extruded upon logical, however, that the acid attacks the surface of the tinned copper conductor on the one hand by virtue of its inherent acid property of reacting upon metal, thereby forming a film of salts of tin 'therearound. Since these salts of tin are soluble in hydrocarbon substances, the second phase of the reaction consisting in the dissolving-of the salts in the coating compound proceeds, while the latter is undergoing vulcanization, resulting, upon completion of the vulcanizing process, in the observed adherence of the insulation to the conductor. The structure thus set up, as indicated on the drawing by the numeral 12, constitutes a bond between the insulation and the core which is practi cally integral with both bodies. A conductor insulated in such manner is able to stand much greater mechanical strains than heretofore without stripping of the insulation therefrom, due to the fact that a considerable portion of the strain is borne by the insulation, and the conductor is relieved to that extent.

Although oleic acid has been specified above as the bonding agent, other organic substances are equally efficacious in promoting the desired reaction and may be used in lieu thereof,

in fact, any of the organic acids such as ill) ly varied in accordance with the established practice in the art. However due to its additional property of promotlng vulcanization, care should be exercised in varying the 6 percentage of acid employed; since, though I the acid when used in smaller quantities has I been found to be a good vulcanizing agent especially when used with basic materials, an excess thereof causes the rubber to harden 10 and be affected deleteriously by the acid promoting deterioration with a e. Permissible limits of variation of oleic acld employed under normal conditions may be accepted as from one to five percent by weight of the compound.

' 1. The method of securing the adherence of a rubber compound to a tinned metallic body which consists in mixing with the com- 3 pound while in a plastic state a quantity of oleic acid, applying the compound to the. metallic body, and vulcanizing the compound thereto.

2. The method of insulating a tinned elec trical conductor which consists in mixing with a rubber insulating compound containing sulphur while in a plastic state a quantity of oleic acid, applyingthe' rubber compound while still in a plastic state to the conductor and vulcanizin the rubber compound there to, causing a lm of the salts of tin to be formed about the conductor, which are thereafter dissolved by the rubber compound.

In witness whereof, I hereunto subscribe my name this 29th day of MayA. D., 1929.

EARL 'GROVER STURDEVANI. 

